Taseko Mines Ltd., through its wholly owned subsidiary Yellowhead Mining Inc., is the 100% owner of Yellowhead's mineral tenures.
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Summary:
The Project is located within structurally complex, low-grade metamorphic rocks of the Eagle Bay Assemblage, part of the Kootenay Terrane on the western margin of the Omineca Belt in south-central BC.
Rocks that underlie the property are primarily of the Eagle Bay Assemblage with a lithological succession interpreted as the Dgn, EBQ, EBA, EBF and EBG units of this group. This succession consists of a series of orthogneisses, metasediments, metavolcanics and metavolcanic clastics respectively, structurally overlain by the Tshinakin limestone unit belonging to unit EBG. Regional structure encompasses a complicated sequence of polyphase deformation consisting of sequences of thrust faulting, intrusion-related folding and faulting, strike-slip and normal faulting all of which imposed a complex alteration and metamorphic fabric on the rocks.
The mid-Cretaceous Baldy batholith cuts this succession at the southern end of the property and a late epidote alteration event relates to this intrusion. (Armstrong and Hawkins, 2009).
Mineralization
The principal area of mineralization on the property is the Yellowhead Copper Deposit (the Deposit). The northeast trending Harper Creek Fault separates the deposit into a west domain and an east domain. In the west domain, chalcopyrite mineralization is primarily in three copper bearing horizons. The upper horizon ranges from 60 m to 170 m in width and is continuous along an east-west strike for some 1,300 m, dipping approximately 30º north. Mineralization within this horizon occurs within felsic and mafic volcanics and volcaniclastic rock units. The middle horizon is not as well developed and is often fragmented. It primarily exists within a graphitic and variably silicified package of rocks that range from 30 m to 40 m in width at the western extent, increasing up to 90 m locally eastward, gradually appearing to blend into the upper horizon. Of the three horizons, this contains strong to intense silicification and localized tension fractures filled with mineralization. The lowest or third horizon has less definition mainly due to a lack of drill intersections. Commonly hosted within mafic to intermediate volcaniclastics and fragmental rocks, it can range from 30 m to 90 m in width although typical intersections are in the 30 m range. These horizons host within felsic and mafic metavolcanics and metavolcaniclastics and generally contain foliation-parallel wisps and bands as the dominant style of sulphide mineralization.
In the east domain, mineralization characterized by high angle, discontinuous, tension fractures of pyrrhotite, chalcopyrite ± bornite is frequently associated with quartz carbonate gangue. This style is common within, but not limited to, the metasedimentary rocks and areas of increased pervasive silicification. Mineralization is not selective to individual units and frequently transgresses lithological contacts throughout the area. Locating mineralized horizons in this area has proven difficult due to multiple east-west trending and northward dipping interpreted thrust faults (or possible reverse faults). At the near surface areas in the south and down-dip to the north, widths of mineralization typically range from 120 m to 160 m. In the central area of the east domain where thrust/reverse fault stacking has been interpreted, mineralization thicknesses typically range from 220 m to 260 m with local intersections of up to 290 m. Mafic metavolcanics and coarse-grained quartz-rich metasedimentary rocks generally contain higher grade copper mineralization.
The primary focus of exploration by YMI on the property has been on the main deposit area and mineralization outside of there is not well known.
Deposit Type
Interpretation of the deposit type is that of a remobilized polymetallic volcanogenic massive sulphide (VMS) deposit, comprising lenses of disseminated, fracture-filling and banded iron and copper sulphides with accessory magnetite. Mineralization is generally conformable with the host-rock stratigraphy as is consistent with the volcanogenic model. Observed sulphide lenses measure many tens of metres in thickness with kilometer-scale strike and dip extents. In 2009, YMI conducted a program of field mapping, sampling, relogging, petrographic examination of existing thin sections and re-assessment of the total digestion geochemical dataset that confirmed the deposit type hypothesis for the deposit (Armstrong and Hawkins, 2009).